I can to calculate the Checksum using the atoi_b16?

[pilar]

Hi, I have 12 string stored in a memory eeprom and I need to calculate the CheckSUM of this string to TX, I am using the atoi_b16 but I can not get the correct value, and here is the String of memory eeprom

38
31
39
35
35
43
30
45
32
30
34
35

Here is my code:

[ckielstra]

read_eeprom returns an int8, not an int16 so you will have to increase the addresses by 1, not 2.

I don't know atoi_b16 but most likely you can do without it.
The string data you have listed, are these decimal or hexadecimal values?

[pilar]

[ckielstra]

Have you fixed the address increasing by 1 instead of 2?

If it still doesn't work you'll have to provide more data.
For the fastest response post a complete working test program. Including input data and the expected CRC value.

[Wayne_]

You have several problems, some are code issues and others are your understanding of the problem.

First as pointed out read_eeprom returns an 8 bit value from the address given, it does not return the address of the string or even the string itself.

Secondly, atoi or atoi16 requires a null terminated string, which takes us back to your first problem.

Next is the data itself, I assume from your description that it is a decimal STRING stored in eeprom so the actual data for the first sting is:-
"38" = (hex) 0x33, 0x38, 0x00 (null terminated)

Next, do you need the actual values for your checksum or can you use the ascii values e.g
"38" instead of using 38 use (dec)51 + (dec)56 = 107 ?
This would mean you don't need to convert the value.

To convert the value is realy easy though. 2 options, read the string and use atoi or read each char and convert yourself.

Next is are all the numbers 2 digits ?
To simplify the problem, why are you storing them as ascii ?

And lastly, your routine maybe flawed, you are generating a 16 bit value and then subtracting that from 0xFF, why ? This may not give you the result you think it is.

[pilar]